This invention relates to saws, and in particular to circular saws of the type comprising a table, a pivot member on the table and a saw assembly pivoted about a pivot axis with respect to the pivot member, whereby said saw assembly carrying a motor driven blade can be plunged into a workpiece supported on the table.
Such saws are known and described in published patent documents such as EP-0133666 and EP-0450400. These saws are useful and have numerous possibilities for enhancement to improve the capacity, capability and efficiency not to mention cleanliness and safety of their arrangements. On the other hand, all these features add complexity and cost, and may render the saw user unfriendly.
The present invention particularly, although not exclusively, relates to saws of the type described above but which in addition have the table mounted in a frame such that the table may be inverted, as by pivoting about an axis, so that the saw assembly is then beneath the table. The table is in addition provided with a slot so that the blade can protrude through the slot to render the saw a bench or table saw. Such saws are known and described in DE-1628992, EP-0502350 and EP-0586172.
Both EP-0133666 and EP-0450400 mentioned above describe saws in which the saw assembly comprises an upper guard and a lower guard for the blade. The upper guard is formed from the housing of the assembly and permanently covers a top part of the blade. A bottom part of the blade is covered by the lower guard but this must be withdrawn in use so that the blade is exposed when required to perform cutting operations.
A handle is disposed on the upper guard by means of which a user can pivot the saw assembly up and down to perform cutting operations on a workpiece supported on the table. Further, if the table has a rotational portion carrying the saw assembly, mitre cuts can also be made in a workpiece on the table.
The lower guard may be opened entirely by an actuating lever disposed on the handle. Alternatively the guard may be opened automatically by pivoting of the saw assembly, there being provided a connection between the guard and the pivot member for this purpose. A further alternative is that the guard may be opened partly by either of these arrangements and only further opened by direct contact with a workpiece.
Means must be provided to bias the saw assembly to a raised upright position when it is at rest so that the user is not required to lift the not-insignificant weight of the saw assembly after completing a plunge cut. Such means is normally in the form of a powerful spring.
Although the upper and lower guards mentioned above provide satisfactory protection for the saw blade when the saw assembly is acting as a plunge or mitre saw, when the table is flipped-over to convert the saw into a bench saw the saw blade is once again exposed. In this configuration, a separate guard must be provided which, in the past, has been mounted on a riving knife of the bench saw each time the saw is used as a bench saw.
It is also known from U.S. Pat. No. 5,060,548 to mount the saw assembly on a rod which can slide through a support mounted on the table. The pivot which carries the motor and saw blade is positioned at one end of the rod and the pivot bracket limits the motion of the rod through the support. Furthermore, all the weight of the motor and saw blade acts on one side of the support, thereby requiring the support to have significant strength.